Yttrium Silicate Coatings for Oxidation Protection of Carbon–Silicon Carbide Composites

Abstract

Yttrium silicate (Y 2 SiO 5 ) coatings complement SiC coatings for protecting ceramic multilayer composite materials based on carbon-fiber-reinforced SiC composites (C-SiC). Thick (100 m), dense Y 2 SiO 5 coatings were prepared by dip coating, using concentrated aqueous slips. The resulting phases were studied by taking into account the simultaneous presence of oxide and non-oxide materials, which affected the chemical stability of the coatings. Thick, mechanically stable coatings were obtained by sintering in carbon crucibles and a SiC bed in an argon-flow furnace. Pure Y 2 SiO 5 coatings completely separated from the SiC substrates. A high percentage of Y 2 Si 2 O 7 was necessary to fit the thermal expansion coefficients and ensure the stability of the coatings. Oxidation resistance of the coated substrates was investigated by isothermal and stepwise oxidation tests.

Structure and possible origins of stacking faults in gamma-yttrium disilicate

“…They are also fully oxidised and do not contain volatile components and thus are suitable for use in highly oxidising environments. For this reason, they have been investigated as possible matrix materials for oxide-oxide ceramic matrix composites [1,2] and as oxidation barrier coatings for non-oxide ceramic matrix composites [3][4][5][6].…”

Oxidation of epitaxial Y(0001) films

“…Especially important is the use of various metal oxides as protective layers against further oxidation or corrosion [3,4]. For the protection of metals a variety of capping mechanisms have been established, such as the chemical vapor deposition of coatings [5] or thick laser coatings [6].…”

Direct Preparation of Y2SiO5Nanocrystallites by a Microwave Hydrothermal Process

“…According to Aparicio and Durán [4], the formation of Y 2 SiO 5 crystallites under solution condition is based on the reaction shown in (1)- (3). During the microwave hydrothermal process illustrated in Figure 6, Y 2 (SiO 3 ) 3 and Y(OH) 3 will be generated in the early period in the reaction.…”

“…Y 2 SiO 5 : Eu 3+ was found to be a promising candidate for coherent time-domain optical memory (CTDOM) applications [3]. Due to its high melting point, low evaporation rate, equivalent thermal expansion coefficient, and low oxygen permeation constant [4], yttrium silicates is considered as one of the best antioxidation coating for C/C composites [5][6][7]. But the preparation technology has great influence on the morphologies and properties of Y 2 SiO 5 [8].…”